The Data Coordinating Center (DDC) will continue to be responsible for all data management and biostatistical analysis in the recently funded extension for the "Growth Failure in Children with Renal Diseases" (GFRD) Clinical Trial. The DCC identifies and controls extraneous sources of variability, ensures the accuracy, reliability, validity and completeness of all anthropometric, nutritional and laboratory data and provides expert analysis and interpretation. The GFRD Clinical Trial is a multi-center, randomized triple-masked control study to determine differences in treatment effect (1, 25-dihydroxyvitamin D3 or dihydrotachysterol) on linear growth and complications of treatment. Eligible patients are initially enrolled in a 6-month Control Period (to provide baseline data and to ascertain compliance) and are then randomized to a Treatment Period for at least 6 months and up to 5 1/2 years. The DCC monitors compliance with the GFRD Manual of Operations, the comprehensive document developed during the planning period, updated as needed and presently used by Clinic Directors, Data Managers and Clinic Dietitians at all participating centers. This is accomplished by daily/weekly telephone contacts, site visits as required and one or two additional Training/Orientation Sessions for all participants. Data recorded on GFRD forms are sent to the DCC, logged in, visually reviewed, entered, verified and edited through "EasyEntry", further edited using SAS then organized and backed up on the VAX through SAS. During the "analysis" year, interim and final analyses of clinical trial data will be presented in several areas. (Three interim analyses have been completed to date: at least one more is scheduled.) Multivariate growth curve analysis will be used to test differences in linear height between treatment groups; multiple regression techniques will be employed in the analysis of reciprocal serum creatinine (and glomerular filtration rates); multivariate proportional hazards analysis will be used to compare treatment complications such as hypercalcemia between groups.